100
3 An Introduction to Surface Waves
Table 3.2: Extreme wind speed and wave heights in various regions of the World
Ocean (adapted from Massel, 1996a)
Extreme value
Region
Wind speed
Wave height
(m/s)
(m)
TR = 30 Y TR = 50 Y TR = 30 Y
Midlatitude zones of the North
48
53
20
Atlantic Ocean
(42-54)
(44-62)
(17-23)
Midlatitude zones of the South
50
55
23
Atlantic and Indian Ocean
(42-58)
(43-67)
(19-27)
Midlatitude and subtropical Pacific;
48
55
21
Midlatitude South Pacific
(40-56)
(43-67)
(18-24)
Tropical zone of the North
39
44
16
Atlantic Ocean
(31-47)
(34-54)
(13-19)
Tropical zone of the South
32
36
14
Atlantic and Indian Ocean
(28-36)
(30-42)
(12-16)
Tropical zone of Pacific and tropical
33
36
12
monsoon zone in Indian Ocean
(29-37)
(30-42)
(10-14)
Equatorial zone
32
35
12
(28-36)
(29-41)
(10-14)
Significant monthly variations are observed in the Westerlies. The highest
wind speeds are found in a broad band between Africa and Australia, where the
largest waves also occur (Young, 1994; Young and Holland, 1996). On the other
hand, in the western region of the Indian Ocean, close to the African coastline,
between Durban and Port Elizabeth, giant waves (freak waves) sometimes occur, even during relatively calm weather. Their front slope is very steep and
the heights of the waves are typically 15-18 m. During a 22 year period (19521973) in this region, eleven ships were sunk or seriously damaged (Davidan and
Lopatukhin, 1978). Two particularly unfortunate cases were the World Glory,
which broke in two and sank in June 1968, and the Neptune Sapphire, which
lost 60 m of its bow section in August 1973. It can only be speculated that
giant waves may account for many of the ships which have been lost without